The present invention generally relates to retractors and pretensioners for seat belts and more particularly to an apparatus that enhances the ability of the retractor to quickly and positively lock subsequent to pretensioner activation.
Emergency locking (ELR) seat belt retractors include a sensing mechanism typically using both a vehicle and web sensor to initiate the lock up of the retractor during an emergency situation such as during a severe brake maneuver or during a collision. Pretensioners are now used to reduce or eliminate slack in the seat belt and typically the shoulder (torso) belt, however, the pretensioner is only activated in a severe collision. Pretensioners typically use springs or pyrotechnic elements to apply forces to the seat belt. A clutch or rotary hub or wheel converts the linearly acting pretensioner force to a rotary force to forcibly reverse rotate the spool and in so doing remove slack about the occupant. After the slack is removed the retractor spool must again be locked extremely quickly to prevent the protraction of the seat belt due to the inertial loads applied thereto by the occupant as the occupant is driven forward in reaction to the deceleration of the vehicle. During the time that the spool is reverse wound by action of the pretensioner a lock dog or lock pawl typically associated with the vehicle sensor, ratchets over closely spaced lock teeth of the spool. A typical pretensioner removes the slack in the seat belt in less than 10 milli-seconds and imparts an extremely high rotational torque and acceleration to the spool. As the spool moves rapidly past the lock dog (lock pawl) the lock dog not only ratchets over the teeth but may also begin to bounce about the teeth. The significance of this bouncing is that the lock dog may not be in the desired position to rapidly lock the spool to prevent protraction of the seat belt upon being loaded by the occupant. The present invention provides a means for positioning a lock pawl or lock dog relative to the lock teeth and insures a rapid lock up.
It is an object of the present invention to provide an improved safety device. An additional object of the invention is to provide a device in which rapid lock up of the retractor is insured after pretensioner operation.
Accordingly the invention comprises: a safety device comprising: a retractor for protracting and rewinding a safety belt to be worn about an occupant, having a lock wheel and an associated lock pawl movable into engagement therewith upon sensing an emergency condition, a sensing mechanism for initiating lock up during certain operational conditions; pretensioner means for winding the spool in a belt winding direction, including a pretensioner and clutch means for converting pretensioner motion to rotary motion. The retractor further includes locking readiness means for providing a secondary mechanism for maintaining the lock pawl in locking readiness to lock against the lock wheel after pretensioner activation and the rotation of the spool in the belt winding direction due to occupant loading. This locking readiness means includes, in one embodiment, a rotatable tie bar wherein the lock pawl is mounted to and rotatable with the tie bar; and activation means for selectively biasing the tie bar subsequent to pretensioner activation in a direction to move the lock pawl against the lock wheel. Various means of biasing the tie bar are disclosed. In an alternate embodiment a secondary lever is used to directly activate a part of a vehicle sensor which biases the sensor into activation thereby moving the lock pawl towards a position of engagement with the lock wheel.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.